Electronically and ionically conducting polymer matrix

ABSTRACT

The present invention provides electronically conducting polymer films formed from photosensitive formulations of pyrrole and an electron acceptor that have been selectively exposed to UV light, laser light, or electron beams. The formulations may include photoinitiators, flexibilizers, solvents and the like. These solutions can be used in applications including printed circuit boards and through-hole plating and enable direct metallization processes on non-conducting substrates. After forming the conductive polymer patterns, a printed wiring board can be formed by sensitizing the polymer with palladium and electrolytically depositing copper.

This appplication is a continuation of pending U.S. patent applicationSer. No. 08/492,235 entitled "Method of Forming ElectronicallyConducting Polymers on Conducting and Nonconducting Substrates" filed onJun. 19, 1995.

FIELD OF THE INVENTION

The present invention relates to conductive polymers and their use inelectronic applications. More particularly, the present inventionrelates to the preparation of polypyrrole and its use in preparingelectronically conducting polymers on conducting and nonconductingsubstrates, such as printed circuit boards. Even more particularly, thepresent invention relates to photosensitive solutions of pyrrole anddirect metallization processes for preparing electronic circuits onnon-conducting substrates.

BACKGROUND OF THE DISCLOSURE

The trend toward miniaturization, integration and automated assembly inthe electronics industry is forcing designers to continually increasethe component density in integrated circuit manufacturing,interconnection and packaging. Current demand for increasingly complexPWBs has resulted in increasingly stringent requirements for allproduction steps. To produce high-quality boards at competitive pricesmeans keeping production costs down. This in turn means less consumptionof environmentally toxic chemicals, reduced number of manufacturingsteps, shorter process times, and a greater need for automation.

The introduction of double-sided, followed by multilayer boards, wasachieved by metallization of plated through-holes with electrolesscopper. For the last 25 years, 98 percent of the PWBs manufactured usedthis technology. However, electroless deposition of copper require's apotent reducing agent, such as formaldehyde--a reported carcinogen. Mostelectroless copper solutions contain cyanide and chelating agents, whichare difficult to remove from waste streams. Besides the normal drag-outassociated with wet processing, "Mail-out" (required to maintainsolution balance and periodic bath changes) renders waste treatment ofelectroless copper far more expensive than electroplated copper.Stripping copper from racks and tanks with nitric acid is anotherenvironmental and waste treatment concern associated with electrolesscopper.

In the conventional subtractive plated-through-hole (PTM process, copperfoil is laminated onto an insulating substrate (typically polyimide,epoxy-fiberglass, etc.). Holes are drilled through the copper-cladlaminate to allow insertion of components. Then the typical smear andetch-back process uses an alkaline permanganate solution followed by ahydrofluoric acid solution to remove resin smear and glass fibers fromthe walls of the holes in preparation for the plating process.

In the conventional process a seed or catalyst, usually a noble metalsalt, is then applied to the circuit board. Next, by means ofelectroless copper deposition about 10-20 microns of copper is depositedon the surfaces of through-hole walls, providing electrical continuityfrom one side of the panel to the other. Electroless copper depositionis a seven-step process with interval rinses with water that becomecontaminated with copper sulfate/EDTA/formaldehyde bath components.Following electroless copper deposition, copper is electrodeposited overthe entire board surface and sensitized walls of through-holes, usuallyto a thickness of 0.001 in.

A negative-, or plating-resist, pattern is then applied and registeredto both sides of the material. Resist covers all areas of the foil wherebase copper conductor is not required, and the surplus conductor willsubsequently be etched off. The panels are imaged in preparation for theactual circuitry pattern by a conventional photolithographic process. Inthis process photoresist is applied as a thin film to the substrate andis subsequently exposed in an image-wise fashion through a photomask.The mask (Mylar) is then removed. The areas in the photoresist that areexposed to light are made either soluble or insoluble in a specificsolvent termed a developer. In the case of a negative resist, thenon-irradiated regions are dissolved leaving a negative image. This isachieved in the development process.

The next plating step is to electrodeposit copper and a thin layer of asuitable etch-resist plating, usually solder or gold. The originalplating resist, screen or photoresist, is removed, and the circuitpattern is defined by etching away exposed copper in a suitable etchant(e.g. ammonium persulfate). During this process, 90% of the copperplating is removed by etching, thus producing large volumes of sludgeand rinse water.

Recently, the U.S. Environmental Protection Agency's Waste ReductionInnovative Technology Evaluation (WRITE) Protection has been establishedin the printed wiring board manufacturing industry in order to performtechnical and economic evaluations of the volumes and/or toxicity ofwastes produced from the manufacture, processing and use of materials.Environmental concerns associated with electroless copper metallization,have fostered interest in direct metallization processes. Despitenumerous attempts over the last 10 years, conversion to a directmetallization process has not gained widespread acceptance, and onlyabout five percent of PWB manufacturers worldwise have eliminatedmetallization by electroless copper.

In addition to the environmental concerns about electroless coppermetallization, circuit board manufacture using this process can requireas many as 15 to 20 steps (including rinses), involving 70 min ofprocessing time. This obviously creates a roadblock for achieving afree-flowing process. Electronics manufacturers have not realized orappreciated the benefits that direct metallization can provide. Theseinclude reduced waste treatment/processing costs, lower chemical costs,improved efficiency/reliablity, and the elimination of a time-consumingprocedure.

Electronically conducting polymers have often been categorized asnon-processable and intractable, because of their insolubility in theconducting form. Only recently has it been shown that polymers such aspolyaniline can be dissolved using functionalized sulfonic acids. Forpolypyrrole, this can be achieved by using its derivatives e.g., poly(3-octylpyrrole)! which are known to be soluble in different solvents,or by treatment in dilute aqueous sodium hypochlorite solutions, ammoniaor mono-, di- or tri-substituted amine (co)solvents. Another method ofsolubilizing polypyrrole is the process of polypyrrole deprotonation inbasic solutions, which causes a transformation of conducting polypyrroleinto a non-conducting polymer of quinoid structure.

The lack of processability of conducting polymer materials, e.g.,solution or melt processing, infusability and poor mechanicalproperties, e.g., ductility, have slowed down their emerging commercialapplications. While electrochemical preparation of conducting polymershas been shown to be the most satisfactory process from the viewpoint offundamental investigations, it is likely to be inappropriate for thelarge-scale industrial production of bulk quantities of these materials.This is particularly true where large molecular entities, e.g.,copolymers or different additives, need to be incorporated intoconducting polymer matrices in order to obtain tailored performancecharacteristics.

In order to compete with more-advanced interconnect systems, such ashybrid circuits and multichip modules (MCMs), future PWBs will have tobe designed so that their size and cost advantages can be used to find awider range of applications. This will require PWBs with increasedconductor density. To accomplish this, finer lines and spaces (<5 mils),smaller vias (<12 mils), thinner multilayer boards (<0.032 in), andimproved insulation resistance will be necessary. Finer lines and pitchwill require high-resolution imaging and precision etching. The presenceof plated-through-holes (PTHs 0.062-0.04 in) and vias (<0.10 in) inever-increasing numbers, will present a challenge in laminating,drilling and metallization.

Consequently, there remains a need for improved direct metallizationprocesses for preparing electronic circuits on non-conductingsubstrates. It would be desirable to have a direct metalization processthat avoids polymer solubility problems, can easily incorporateadditives, does not depend upon electroless-copper plating, minimizeshazardous chemicals and copper plating solutions, requires fewer processsteps, provides simplified through-hole metallization, and facilitatesincreased conductor densities.

SUMMARY OF THE INVENTION

The present invention provides a method for forming an electronicallyconducting polymer on a substrate comprising the steps of forming asolution comprising a pyrrole monomer and an electron acceptor, whereinthe molar ratio of pyrrole:electron acceptor is between about 0.5 andabout 20; applying a film of the solution onto a substrate;photopolymerizing portions of the film to form electronically conductingpolypyrrole; and optionally washing the unpolymerized portion of thefilm from the substrate and activating the polypyrrole with palladiumbromide. The substrate may be either conducting or nonconducting andeither rigid or flexible.

The electron acceptor is selected from the group consisting of silversalts, e.g., AgNO₃, AgClO₄ and AgNO₂, with the most preferred beingAgNO₃. The solution may further comprise a photoinitiator, anothermonomer such as aniline, a flexibilizer selected from the groupconsisting of polyethylene glycol diglycidyl ether, dodecyl sulfate anddodecylbenzene sulfonate.

The invention further includes a method of forming an electronic circuiton a substrate comprising the steps of forming a solution comprising apyrrole monomer and an electron acceptor; applying a film of thesolution onto the substrate; photopolymerizing portions of the film toform electronically conducting polypyrrole; washing the unpolymerizedportion of the film from the substrate; activating the polypyrrole withaqueous palladium bromide; and electrodepositing copper onto theactivated polypyrrole. This method is particularly well suited to directmetallization of printed wiring boards having through-holes in very fewsteps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating the dependence of conductivity on thetype and concentration of dopant anions present in photopolymerizablepyrrole-based formulations;

FIG. 2 is a graph illustrating the dependence of electrical resistanceof photopolymerized polypyrrole films on the electron acceptor:monomermole ratio in the starting formulation;

FIG. 3 is a graph illustrating the dependence of curing time on theconcentration of photoinitiator;

FIG. 4 is a graph illustrating the dependence of conductivity onphotoinitiator concentration;

FIG. 5 is a graph illustrating the dependence of curing time on theamount of dodecyl sulfate used as flexibilizer;

FIG. 6 is a graph illustrating the dependence of curing time andconductivity on the amount of dodecyl sulfate used as flexibilizer;

FIG. 7 is a graph illustrating the dependence of resistance ofphotopolymerized polypyrrole films on the ratios of pyrrole:anilinemonomers;

FIG. 8 is a photograph of alumina substrates with laser patterned linesof electronically conducting polypyrrole;

FIG. 9 contains scanning electron micrographs of the cross-sections ofpolypyrrole fims formed electrochemically and photochemically;

FIG. 10 contains scanning electron micrographs of the surfaces ofpolypyrrole fims formed electrochemically and photochemically;

FIG. 11 is a flow chart comparing the steps of conventional PWBfabrication with those of the present invention;

FIG. 12 is a photograph of black conducting polypyrrole lines on afiberglass/epoxy PWB substrate patterned using UV illumination through ashadow mask, wherein one line has been electrodeposited with copper; and

FIG. 13 is a photograph of a copper-on-polypyrrole plated 0.025 inchdiameter through-hole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a novel process for using conductingpolymers for direct metallization of nonconducting surfaces which iscapable of metallizing both PWB conductor lines and through-holes. Theprocess is highly compatible with lithographic processes used inmanufacturing PWBs. The proposed process satisfies the criteria requiredfor designing future PWBs: (a) environmentally conscious manufacturing,and (b) high-resolution conductor line imaging.

The formulations of the present invention include a salt that servesboth as an electron acceptor for oxidation of the monomer(s) and as adopant to preserve electroneutrality in the oxidized polymer. Preferredelectron acceptors undergo very slow oxidation of the monomer in thedark (1-2 days) and have the highest conductivities.

Polypyrrole (PPY) can be chemically prepared using inorganic (Fe³⁺ andCu²⁺ ions) or organic (chloranil) electron acceptors. When theseinorganic acceptors are added to pyrrole-containing solutions a powderypolymer material results almost immediately after the addition.Therefore, cations having too high an oxidation potential are notsuitable for photopolymerization of polypyrrole. Several attempts weremade to use organic electron acceptors, but photopolymerization of blackconductive PPY films was unsuccessful. It has been shown that electronacceptors with proper oxidation potential (e.g. Ag⁺, Fe³⁺ or Cu²⁺ ions)and dopant (e.g. NO₃ ⁻, BF₄ ⁻, tosylate, etc.) play a decisive role indetermining the conductivity of the conducting polymer film. Thepreferred electron acceptors are the silver salts (such as AgNO₃, AgClO₄and AgNO₂), with the most preferred being silver nitrate, AgNO₃.

Molar ratios of monomer to electron acceptor ranging between about 2 andabout 100 are effective for producing electronically conductive polymerfilms. However, the electrical conductivity of the polymers decreaseswith decreasing concentration of electron acceptor (increasing monomerto electron acceptor ratio).

A polymer network can be formed by promoting the polymerization of amonomer, oligomer, or mixtures of monomers and/or oligomers.Polymerization is a chain reaction that can develop very rapidly,especially when intense UV radiation is used to produce the initiatingspecies. This UV-curing reaction leads ultimately to a three-dimensionalpolymer network. Since most of the monomers or oligomers commonlyemployed do not produce initiating species with a sufficiently highyield upon UV exposure, it is preferred to introduce a photoinitiatorthat will allow the polymerization to start. A typical UV-curableformulation, therefore, will contain two basic components: (i) aphotoinitiator, and (ii) a monomer, oligomer, or a mixture of monomersand/or oligomers.

The choice of the photoinitiator is of prime importance in light-inducedpolymerizations, since it directly governs the cure rate. A suitablephotoinitiator system must possess high absorption in the emission rangeof the light source. The photoinitiator must also form an excited statehaving a short lifetime to avoid quenching by oxygen or the monomer andsplit into reactive radicals or ionic species with the highest possiblequantum yield. Other factors to be considered in selecting the properphotoinitiator include solubility in the monomer, storage stability andthe nature of the photo-products, which should not be colored, toxic orinduce some degradation of the polymer upon aging. Photoinitiators canbe classified into three major categories, depending on the kind ofmechanism involved in their photolysis: (i) radical formation byphoto-cleavage; (ii) radical generation by hydrogen abstraction, and(iii) cationic photoinitiators.

Cationic photoinitiators have proven to be particularly useful in thephotopolymerization of polypyrrole from pyrrole monomers in solution.Besides their specificity, cationic-initiated photopolymerizations havethe advantage of being insensitive to atmospheric oxygen. In the absenceof nucleophilic reagents, the chain reaction will thus continue todevelop after the illumination has ceased and provide a beneficialpost-cure effect that can be enhanced by thermal treatment. Thepreferred post-photopolymerization thermal treatment involves heatingthe polymer at temperatures between about 80 and about 120 degreesCelsius for about three hours, with the most preferred temperature beingabout 100 degrees Celsius.

Thermally stable photoinitiators for cationic polymerizations ofcommercial significance include the onium salts, such astriarylsulfonium and diaryliodonium, with complex metal halide anions. Akey feature of these photoinitiators is the low nucleophilicity of theanions which reduces termination processes and allows ambienttemperature cationic polymerization to proceed. The absence of airinhibition represents a distinguishing feature of cationic, as comparedto radical, polymerization.

The photoinitiators investigated included a titanocene radicalphotoinitiator (such as IRGACURE™ 784 available from Ciba Geigy, locatedin Ardsley, N.Y.), a cationic ferrocinium photoinitiator (IRGACURE™ 261available from Ciba Geigy, located in Ardsley, N.Y.), triaryl sulphoniumPF₆ ⁻ salts (such as CYRACURE™ 6990, available from Union Carbide,located in Danbury, Conn.) triaryl sulphonium SbF₆ ⁻ salts (such asCYRACURE™ 6974, available from Union Carbide, located in Danbury,Conn.). The photoinitiators are preferrably added to the monomer inamounts less than about 8 weight percent, with the most preferredamounts being between about 0.2 to about 0.8 weight percent.

Photopolymerization of pyrrole alone, or pyrrole mixed with aphotoinitiator such as titanocene, yields a transparent yellow filmexhibiting insulating properties. Resistances of over 20 MΩ are measuredby an ohmeter. When AgNO₃, an electron acceptor, is dissolved into thepyrrole prior to curing, a black polymer film characteristic ofconducting polypyrrole is formed.

In general, both electropolymerized and photopolymerized polypyrrolefilms suffer from poor mechanical properties. They lack flexibility,either as stand alone films or as coatings. Three approaches have beenfound to improve the mechanical properties of photopolymerizedpolypyrrole: (i) incorporating large amphiphilic (surfactant) organicanions into the polypyrrole structure, (ii) photo-copolymerizing asuitable comonomer material with pyrrole, and (iii) including commercialflexibilizers. The preferred surfactants are large anionic surfactants,such as the sodium salts of dodecyl sulfate (DDS) and dodecylbenzenesulfonate (DDBS). The preferred comonomer is aniline. The preferredflexibilizer is polyethylene glycol diglycidyl ether.

In accordance with the present invention, formulations can include amixture of monomers which can be photopolymerized to form copolymers.While photo-copolymerizations can be achieved with many monomerpairings, the preferred monomer pairs for the lithographic production ofan electronically conducting copolymer on a non-conducting substrate arecomprised of: (i) pyrrole in combination with: (ii) a sub-stoichiometricamount of silver nitrate (molar ratio of pyrrole to silver nitrate is8:1) and with (iii) fifteen mole percent aniline relative to pyrrole.The mixed monomer formulation is then diluted with an equivalent volumeof acetonitrile to provide good contact with the substrate.

The components of photopolymerizable solutions are mixed in a glass vialthat excludes the penetration of light. The solutions are then sonicatedto help dissolution and homogenization of the formulation. Since a slowchemical polymerization of pyrrole takes place over a period of one totwo days in the presence of Ag⁺ ions, it is preferred that freshphotopolymerizable formulations be prepared immediately prior topolymerization.

A thin layer of the formulation is then cast and evenly spread on thesurface of a selected substrate typically having a surface area ofbetween about 1 and about 4 square centimeters (cm²). The preferredmethods of spreading the formulation over the substrate to achieve athin layer having uniform thickness include brush coating, spraying,dipping and spin coating, with the most preferred method being spincoating.

After casting of the photopolymerizable solution onto a substrate andformation of an air-dried nonconducting film, the oxidation process isinitiated by irradiation. The preferred irradiation methods are thosewhich selectively expose only discrete regions or lines on the coatedsubstrate, such as exposure by ultraviolet light through a contact mask,direct laser imaging, or electron beam imaging. Using these methods,thin polymer patterns (lines and through-holes) are readily polymerizedon various conducting and nonconducting substrates. Multiplecoating-curing cycles (up to 10 layers) can be carried out in order toproduce thick uniform films.

Photopolymerizations according to the present invention can beaccomplished with a 200-watt mercury-xenon lamp focused through a lensvertically downward onto a circular area of less than one centimeterdiameter. All the optical accessories should be made of fused silica inorder to pass high energy UV as well as visible light.

The present invention uses irradiation as the driving force to induceelectron transfer from the monomer species in a cast solution film tothe electron acceptor, also present in the formulation. As theconcentration of oxidized polymer increases, coupling between theoxidized monomer units begins. This process continues, resulting ingrowth of the conducting polymer chains. Since the polymer is oxidized,the anion present in the formulation intercalates into the polymer,maintaining electroneutrality.

The photopolymerization process does not require a conducting substratefor deposition to take place, and conducting polymer films and/or linesof various thickness, typically between about 5 and about 300 micronscan be readily photopolymerized on typical PWB substrates(fiberglass/epoxy, polyimide) and MCM (alumina) as well as on metals,ceramic, silicon, GaAs, glass, paper, Teflon, Mylar and polystyrenesubstrates. The process of the present invention is much simpler thantechniques known in the art and offers a high potential and flexibilityfor adaptation to a variety of PWB technologies.

The photopolymerization process of the invention includes the followingsteps:

(i) a photopolymerizable formulation is applied on a substrate;

(ii) after air-drying, a dry negative prepolymer film is exposed tolaser light, an electron beam or to a UV lamp through a shadow mask;

(iii) the illumination induces photopolymerization of the prepolymerfilm at exposed areas rendering the exposed areas insoluble; and

(iv) the non-polymerized (non-illuminated) areas are washed off with anenvironmentally benign solvent (acetone) or water, leaving a pattern ofconducting polymer lines.

The main advantage of the photopolymerization process, compared toelectrochemical and/or chemical polymerizations, is that it allowsproperties of conducting polymer films to be easily designed andoptimized by incorporating molecular species into the, polymerstructure. For example, it is possible to change the conductivity of thepolymer by controlling the amount of the electron acceptor and dopantanions present in the formulations. The same oxidatively coupledcationic polymer is formed through photopolymerization as throughelectrochemical polymerization, except that the anion/monomer ratio ismuch higher (1:1.3) compared to that found in electrochemically formedfilms (1:4). This is a desirable feature because with more anions in thepolymer matrix, more charge can be introduced onto the polymer chainsand, consequently, higher conductivities may be achieved.

One embodiment of the invention provides for a composition having anelectronically conducting polymer matrix comprising a polymer selectedfrom the group polypyrrole, polyaniline, polythiophene and mixturesthereof, and an ionically conducting polymer homogeneously distributedin the polymer matrix.

Preferably, the electronically conducting polymer comprises polypyrrole.The polypyrrole is photopolymerized from pyrrole and a silver salt in apyrrole:silver salt molar ratio between about 2:1 and about 100:1preferably about 8:1. Silver nitrate is the most preferred silver salt.Silver grains are distributed throughout the polypyrrole.

The ionically conducting polymer is preferably a perfluorinated sulfonicacid polymer. The perfluorinated sulfonic acid polymer concentration isless than about 10 weight percent of the polymer matrix.

In another embodiment of the present invention, there is provided apolymer matrix that is electronically and ionically conducting. Thepolymer matrix comprises polypyrrole that is photopolymerized frompyrrole and silver salt; and a perfluorinated sulfonic acid polymer thatis incorporated generally homogeneously into the photopolymerizedpolypyrrole. The weight ratio of perfluorinated sulfonic acid polymer topolypyrrole is less than about 0.1. It is preferred that the pyrrole andsilver salt are photopolymerized in a pyrrole:silver salt molar ratiobetween about 2:1 and about 100:1 most preferably about 8:1. Silvernitrate is the most preferred silver salt. After photopolymerization,silver grains are distributed throughout the polypyrrole.

A process for making a composition that is electronically and ionicallyconducting is also provided. The process comprises the steps of: a)providing a solution comprising pyrrole and an electron acceptor in apyrrole:electron acceptor molar ratio between about 2:1 and about 100:1;b) adding a solubilized perfluorinated sulfonic acid polymer that isionically conducting into the solution, wherein the weight ratio ofperfluorinated sulfonic acid polymer to polypyrrole is less than about0.1; and c) polymerizing the pyrrole to form a polypyrrole matrix havingperfluorinated sulfonic acid polymer distributed therein.

EXAMPLE 1

A separate investigation involving both photopolymerization and thermalpolymerization processes was performed on samples having two differentelectron acceptor salts, AgNO₃ and AgTs, at rather low concentrations(pyrrole:electron acceptor=50:1). Four samples were cured at the sametime either thermally or by photopolymerization. Curing times weredetermined by observing the solidification of the surface and byapplying a simple pencil hardness test, often used in the polymercoating industry for semiquantitative determination of curing quality.The results are summarized in Table 1.

                                      TABLE 1    __________________________________________________________________________    COMPARISON OF PHOTOPOLYMERIZED AND THERMALLY POLYMERIZED POLYPYRROLE    FILMS (PYRROLE/ELECTRON ACCEPTOR MOLAR RATIO WAS 50:1; PHOTOINITIATOR:    3 wt % IRGACURE 261)                  AgNO.sub.3      AgTs    LAYER         ELECTRON PHOTO-  THERMALLY                                  PHOTO-  THERMALLY    NUMBER         ACCEPTOR POLYMERIZED                          POLYMERIZED                                  POLYMERIZED                                          POLYMERIZED    __________________________________________________________________________    FIRST         CURE     68      69      68      69    LAYER         TEMPERATURE         °C.         CURING TIME                   2      3.5      3      18         min         POLYMER FILM                  smooth, black,                          incomplete                                  smooth, green-                                          incomplete         APPEARANCE                  brittle coverage,                                  black, brittle                                          coverage                          gray-black,     gray-green black,                          rough, brittle  rough, brittle    FIFTH         CONDUCTIVITY                  9.7 × 10.sup.-3                          3.8 × 10.sup.-2                                  4.1 × 10.sup.-4                                          6.0 × 10.sup.-5    LAYER         S cm.sup.-1         CURE     68      68      67      68         TEMPERATURE         °C.         CURING TIME                   7      8        9      20         min         POLYMER FILM                  smooth, black,                          gray-white-                                  smooth, green-                                          gray-white-         APPEARANCE                  brittle black, rough,                                  black, brittle                                          black, rough,                          brittle         brittle    __________________________________________________________________________

Thermally cured polymer films, either with AgNO₃ or AgTs as electronacceptor, were of very poor quality, rough and Jacked a uniform color,indicating nonhomogeneous polypyrrole films. Thermal curing of the firstlayer proceeded with incomplete coverage of the exposed substratesurface and curing resembled that of simple drying of the solution. Onthe other hand photopolymerization of the first layer resulted in acompletely covered substrate surface. When more layers were added,curing times became longer, because of the penetration of freshly addedformulation into the existing layers. Curing times for films wheresilver tosylate was added as the electron acceptor salt were longer thanfor AgNO₃ -containing samples. This was expected, because diffusion oflarger (organic) anions into polymer films being formed (in order tosatisfy the neutrality of an oxidized polymer) is much slower than forsmaller anions, like nitrates. Thermal curing, required 2-3 times longercuring times than the process of photopolymerization. This is evidentespecially where tosylates are used as electron acceptors.

From the results of this experiment it is evident that the photochemicalpolymerization process proceeds faster than thermal polymerization andproduces more smooth and uniform polypyrrole films. The thermalpolymerization process is obviously different in nature, possibly basedon a chemical polymerization mechanism at elevated temperatures, leadingto the formation of a partially silver-filled non-conducting polypyrrolematrix.

EXAMPLE 2

In order to improve the mechanical properties of PPY films threedifferent electron acceptor salts were investigated: AgNO₃, AgTs andAgBF₄. It has been reported that incorporation of tosylate anionsimproves the mechanical properties of electrochemically formed PPYfilms. Thus, these three electron acceptor salts were added tophotopolymerizable formulations using pyrrole: acceptor molar ratiosranging from 100:1 to 4:1, the latter being closest to the ratio ofpyrrole monomer to positive charge found in electrochemicallypolymerized films. FIG. 1 shows the dependence of electricalconductivity on the concentration of electron acceptors (AgNO₃ and AgTs)added to the formulations. Both curves exhibit a maximum conductivityvalue of approximately 0.1-0.3 S cm⁻¹ at pyrrole:salt molar ratiosbetween about 3:1 and about 8:1. A steep decrease in conductivityoccurred at molar ratios higher than 15:1. In the case of AgTs, at lowadded salt concentrations, the conductivities were several orders ofmagnitude lower than those for polymer films photopolymerized withAgNO₃. The data shown in FIG. 1 includes films of different thicknesses,where all of them were photopolymerized and then peeled off from Alsubstrates. Although the thinner films were less brittle and lessfragile, no improvement in mechanical properties was observed for filmsphotopolymerized with tosylates.

In experiments performed involving different substrates it was foundthat comparisons between photopolymerized polypyrrole films were bestachieved if polystyrene was used as the substrate, and if the filmsunder investigation were cured at the same time, which assured the samecuring conditions. Polystyrene showed satisfactory wettability for awhole range of film compositions used.

In Table 2 results are given for PPY films photopolymerized usingdifferent silver salts, and their mixtures, added at pyrrole:salt molarratios of 8:1. All the films yielded conductivity values within an orderof magnitude of each other (approximately 0.1 to 0.4 S cm⁻¹), except inthe case of AgBF₄ which displayed a conductivity value two orders ofmagnitude lower. AgBF₄ -containing films possessed the poorestmechanical properties, and required the longest curing times forcomplete curing. When mixed with AgNO₃ in equimolar concentrations, butkeeping the total pyrrole/salt ratio constant (8:1), the conductivity ofpolypyrrole films improved and approached the values measured for AgNO₃alone.

From the data presented in FIG. 1 and Table 2, it was concluded thatAgNO₃ added to photopolymerizable formulations in amounts correspondingto 10-15 mol %, provide the necessary electron acceptor properties forphotopolymerization to take place, and gives the amount of NO₃ -anionsrequired for charge balance inside the polymer. Thus, AgNO₃ is theoptimal choice of electron acceptor for the photopolymerization ofpyrrole.

                                      TABLE 2    __________________________________________________________________________    CONDUCTIVITY OF PHOTOPOLYMERIZED PPY FILMS CONTAINING    DIFFERENT ANIONS (ELECTRON ACCEPTOR: Ag.sup.+ ; PHOTOINITIATOR: 3    wt % IRGACURE 261; PYRROLE/SALT RATIO = 8:1).    ELECTRON           STAND ALONE FILMS                           FILMS ON POLYSTYRENE    ACCEPTOR           CONDUCTIVITY                    THICKNESS                           CONDUCTIVITY                                    THICKNESS    SALT   S cm.sup.-1                    mm     S cm.sup.-1                                    mm    __________________________________________________________________________    AgNO.sub.3           0.425    62     0.158    34    AgTs   0.197    88     0.179    53    AgBF.sub.4             0.0018   57    AgNO.sub.3 \AgTs           0.212    168    AgNO.sub.3 \AgBF.sub.4           0.375    51    __________________________________________________________________________

EXAMPLE 3

A series of experiments were performed to examine the electricalresistance of photopolymerized polypyrrole films as a function ofmonomer/electron acceptor mole ratio in the starting formulation. A moleratio range of 20:1 to 0.5:1 (pyrrole:silver nitrate) was investigated.The solutions were prepared in one ml of pyrrole monomer and varyingamounts of silver nitrate. Pyrrole films of constant thickness (ca. 60microns) were produced. A minimum in resistance (Van der Pauw method) ofca. 80Ω was observed at a 1:1 mole ratio of monomer to silver nitrate.Results shown in FIG. 2 demonstrate that by simple adjustment of theconcentration of starting formulation components (monomer and electronacceptor) an order of magnitude change in resistance could be obtained.

EXAMPLE 4

Simple tests of thick film curing were performed by simultaneousillumination of formulations containing photoinitiators added at 3 wt %to an 8:1, pyrrole:AgNO₃ solution. Exposure to UV light was broughtabout from the top of miniature glass vials (0.7 cm dia. and 1.1 cmheight) containing different photoinitiators. The process ofphotopolymerization was closely followed under low illuminationconditions (corresponding to a temperature of 30°-32° C.), in order todetermine the changes taking place during photopolymerization. In allfour vials the polymerization process went through different stageswhich affected the color of the bulk and/or surface layers of theformulations and the speed of solidification. From this simpleexperiment it was observed that cationic photoinitiators exhibitedfaster curing rates than radical photoinitiators. Especially, Irgacure261 demonstrated better curing (in line with weak absorption of 366 nmlight), as evidenced by a deeper and more homogeneous blackening andsolidification of the entire formulation volume in the glass vial.

Although the choice of photoinitiator between triaryl-sulfonium saltsand the ferrocinium photoinitiator, all three being cationicphotoinitiators, was not conclusive, the ferrocinium photoinitiator ismore suitable for photopolymerization of pyrrole because it allowsdeeper light penetration through the black solidified surface layer.Ferrocinium photoinitiators have been found to be successful for thephotopolymerization of epoxides, which have been used in this work aspotential copolymers with polypyrrole (see later).

The effect of ferrocinium photoinitiator concentration on the curingtime of PPY films is shown in FIG. 3. Formulations containing increasingamounts of photoinitiator were applied at different thicknesses on Aland glass substrates, and were cured simultaneously. Curing time wasdetermined by observing solidification and by the pencil hardness test.Increasing the amount of photoinitiator from 1 to 8 wt % decreased thecuring time by approximately a factor of two. FIG. 4 shows thatincreasing amounts of photoinitiator present in the films causes aslight decrease in conductivity.

EXAMPLE 5

Organic anions chosen were DDS (dodecyl sulfate, sodium salt) and DDBS(dodecyl-benzene sulfonate, sodium salt). They were added to the alreadyoptimized formulation to yield the highest conductivity, i.e.,pyrrole:AgNO₃ ratio of 8:1 and 3 wt % of Irgacure 261 photoinitiator.Amounts added to the formulation are expressed as pyrrole/surfactantmolar ratios. Polypyrrole films where photopolymerized from theseformulations under different illumination conditions and on varioussubstrates. A postcure thermal treatment at the highest lamp irradiancewas applied after photocuring. This is recommended by Ciba-Geigy forcompletion of curing processes when Irgacure 261 photoinitiator is used.

Photopolymerization along the area of the substrate covered by theformulation was followed by observing black solidifying zones smoothlyspreading on the substrate. It was evident that these additives helpeddiffusion of polymerizing components in the thin formulation layer.Curing was generally slower than for the films without surfactantadditives. Films obtained showed a significant improvement in mechanicalproperties. They were very flexible compared to the films that did notcontain surfactant additives. It was possible to bend these films,whether coated on an aluminum sheet or on polystyrene, through anglesgreater than 90° without breaking them. Additives acting as surfactantsgreatly improved the adherence to the substrate. More importantly, filmsthus formulated retained good conductivity. DDBS was less soluble inpyrrole and gave rise to films of lower flexibility when compared tofilms with DDS as additive. Table 3 compares conductivities for DDS- andDDBS-containing films, added to pyrrole:surfactant molar ratios of 15:1.

                                      TABLE 3    __________________________________________________________________________    CONDUCTIVITY OF PHOTOPOLYMERIZED PPY FILMS WITH LARGE ORGANIC    ANIONS AS FLEXIBILIZERS (PYRROLE/AgNO.sub.3 = 8:1; PYRROLE/SURFACTANT =    15:1; PHOTOINITIATOR; 3 wt % IRGACURE 261; CURING TIME: FAST, 1.9 W    cm.sup.-2    WITH THERMAL POSTCURE: 2.3 W cm.sup.-2).    ADDITIVE DDS             DDBS    SUBSTRATE             CONDUCTIVITY                      THICKNESS                             CONDUCTIVITY                                      THICKNESS    MATERIAL S cm.sup.-1                      mm     S cm.sup.-1                                      mm    __________________________________________________________________________    STAND ALONE             0.21     163    0.20     215    STAND ALONE             0.51      61    0.59     75    STAND ALONE             0.134    224    PY/AgNO.sub.3 = 5/1             0.48      39    0.32     62    POLYSTYRENE             smooth, black,  smooth, black,    POLYMER FILM             curing time: 1.3 min/layer,                             curing time: 2 min/layer,    APPEARANCE             very flexible   flexible    __________________________________________________________________________

FIGS. 5 and 6 show variations in curing time and conductivity of filmsphotopolymerized with different concentrations of DDS additive. It waspossible to follow the curing progress at two stages: corresponding tosurface solidification and when curing was completed. Both plots exhibitthe same slope, showing that the curing time is longer with increasingamount& of DDS in the films. Films with higher concentrations ofsurfactant additive became soft. The electrical conductivity of thefilms was within the range 0.1-0.5 S cm⁻¹. A minimum in electricalconductivity, evident at ratios between 30:1 to 50:1, is probably due toan artifact in that the resistivity probe tips penetrated into the softfilms at ratios greater than 30:1 and hence, displayed conductivityvalues higher than those for the films of measured thickness. It wasfound that films containing between 10:1 and 20:1 of pyrrole:DDSadditive, possess the greatest flexibility and conductivity.

EXAMPLE 5

A series of experiments were performed to examine the electricalresistance of polymer films photopolymerized from mixtures of pyrroleand aniline monomers. Solutions of silver nitrate (AgNO₃), pyrrole, andaniline were prepared in one ml of acetonitrile. Equivalent molaramounts of AgNO₃ and various proportions of pyrrole and aniline wereprepared in a large volume excess of acetonitrile (about 500 volumepercent).

The solutions were deposited with a brush to coat a masked ceramicalumina substrate and cured immediately. Two to three successive layerswere built up on the alumina with a thickness between 20 and 160microns. The polymer samples were cured in 1 sq cm areas and contactsfor resistance measurements were drawn with a silver paint. Resistivity(Ω-cm) was calculated for each polymer film prepared in duplicate by thevan der Pauw method. FIG. 7 shows the relationship between thepyrrole/aniline monomer ratio and resistivity of the resulting films.

The results show that the presence of a comonomer in thephotopolymerization formulation can be utilized to change and/or controlthe resistance of the resulting mixed conducting polymer film. A maximumin resistance was obtained in the molar ratio range between about 35 andabout 70 percent (%) of aniline present in the formulation. At higherratios (>70%) the resistance decreased. Lowest resistances were foundfor films with little or no aniline present. However, polymer films withaniline present in the formulation exhibited smoother film surfaces. Thesame results were obtained using fiber-glass epoxy and polyimide PWBsubstrates.

EXAMPLE 6

A series of experiments were performed under the conditions described inExample 5, for a various copolymer materials such as an aqueous acrylicresin, bisphenol A diglycidyl ether, and perfluorinated sulfonic acid.The results are given below in Table 4.

The waterborne acrylic resin did not undergo successful copolymerizationwith pyrrole. It was possible to make a film only if it was added atamounts less than 4 wt %, however, resulting in reduced conductivity.Acrylic resins undergo very little cationic polymerization (mostlyradical induced), which is incompatible with the photo-polymerization ofpyrrole.

Copolymerization of pyrrole with bisphenol A diglycidyl ether, whichundergoes a cationic photopolymerization mechanism, resulted in goodfilms covering a large range of pyrrole/copolymer ratios from 10:1 to1:1. It may be noted that on using the ferrocinium photoinitiator andbisphenol A diglycidyl ether alone, a yellow nonconducting film wasobtained. Conductivities of PPY/epoxide copolymers were approximately anorder of magnitude lower than that of PPY films without a copolymer.Increasing the amount of epoxy copolymer up to a ratio of 1:1 resultedin an order of magnitude decrease in conductivity as shown in. Table 4.PPY/epoxide copolymers possessed good flexibility and exhibitedsoftness, the latter increasing with higher amounts of epoxide copolymeradded. Also, these films adhered very well to metallic and nonmetallicsubstrates, and it was difficult to peel them off, partly due to theirsoftness.

                                      TABLE 4    __________________________________________________________________________    CONDUCTIVITY OF PPY FILMS PHOTO-COPOLYMERIZED WITH DIFFERENT RESINS    (PYRROLE/AgNO.sub.3 = 8:1; PHOTOINITIATOR: 3 wt % IRGACURE 261; CURING:    DIFFERENT CONDITIONS; AVERATE 1.2 W cm.sup.-2 ; FOR ARALDITE, 2.1 W    cm.sup.-2 AND    THERMAL POSTCURE AT 2.3 W cm.sup.-2.    COPOLYMER            % (w/w)  THICKNESS                            CONDUCTIVITY    MATERIAL            OF COPOLYMER                     mm     S cm.sup.-1                                     COMMENT    __________________________________________________________________________    MAINCOTE            50                       no polym., yellow precipitate    HG 54 D (1:1)    MAINCOTE             4       65     0.074    black, smooth, max. copol.    HG 54 D                          conc = 4 wt %    MAINCOTE             4       119    0.072    black, smooth, max. copol.    HG 54 D                          conc = 4 wt %    ARALDITE 502            10       121    0.086    black, smooth, flexible    (on polystyrene)            14       74     0.022    longer curing needed            20       159    0.0092   at high lamp power    (on glass)            14       41     0.063    t > 10-15 min/layer            20       20     0.044    t > 10-15 min/layer            34       14     0.015    t > 10-15 min/layer            51       12     0.0068   t > 10-15 min/layer    NAFION   5       64     0.53     black, smooth, flexible            10                       to resistive, voltage transients                                     show saturation    __________________________________________________________________________

Photocopolymerization with relatively low concentrations ofperfluorinated sulfonic acid appeared to be successful, and highelectronic conductivities were retained. At higher concentrations ofNAFION copolymer (10 wt %), the conductivity values were irreproducibleand decreased, indicating a structure of mixed conducting pyrrole andnonconducting (or ionically conducting) NAFION.

EXAMPLE 7

A test was performed using a high resolution laser and an electron-beamfor the patterning of conducting polypyrrole lines.

Referring now to FIG. 8, alumina substrates, (bottom row, one inch byone inch substrates), have laser patterned lines formed from a 4:1pyrrole:silver nitrate formulation spun at 500, 300, and 1000 RPM,respectively. Each alumina substrate contains several sets of 3-5 linesobtained with a different number of laser beam passes. Aluminasubstrates shown in the top row (one inch by one inch substrates) havelaser patterned lines using a 8:1 pyrrole:silver nitrate formulationspun at 500 and 1000 RPM, respectively. The small alumina substrate hasa patterned line formed from a 4:1 pyrrole:silver nitrate formulationphotopolymerized by a 10 nm wide electron beam. Each of the formulationscontained acetonitrile.

The parameters (beam current, beam sweep rate, number of passes) werevaried for each set of exposures to test the photopolymerizationprocess. Line widths obtained using argon ion laser imaging were ca 100microns..

An electron beam was used to fabricate both narrow lines (down to 1.5microns wide) and wide lines (80 microns wide), using the same exposureparameters, but two different techniques. The narrow lines werefabricated using a step and repeat technique, (i.e. the electron beamwas moved across the sample and the sample moved between exposures) toform a number of parallel lines with approximately equal linewidths andspacing. The wide lines were fabricated by exposing narrow linestogether (side by side), with sufficient overlap to eliminate anyvisible rastering under SEM examination.

EXAMPLE 8

Scanning electron micrographs of fracture surfaces of thickphotopolymerized (70 micron) and electropolymerized (67 micron)polypyrrole films are shown in FIG. 9. It can be seen from FIG. 9(a)that electrochemically prepared polypyrrole is dense, non-fibrillar andvolume-filling. The photopolymerized polypyrrole material of FIG. 9(b)is surprisingly compact, but more open-structured and contains somevoids.

Scanning electron micrographs at two magnifications of the outersurfaces of electropolymerized and photopolymerized polypyrrole filmsare presented in FIG. 10. Now referring to FIGS. 10(a) and 10(c), anelectrochemically prepared polypyrrole is shown to have nodular or"cauliflower" structures that are consistent with a nucleation/dendriticfilm growth mechanism. This surface topology is frequently observed forelectrochemically prepared polypyrrole materials. In contrast, thesurface topography for the photopolymerized polypyrrole films shown inFIGS. 10(b) and 10(d) was rather featureless, being smooth and flat. Asobserved in the micrograph of the fractured surface of photopolymerizedPPY in FIG. 9(b), a large number of evenly distributed Ag grains ofsurprisingly uniform size can be seen also on its outer surface. In thehigher magnification electron micrograph FIG. 10(d), the bright,reflective, spherical Ag particles were determined to be 1 μm or less indiameter. Also in this micrograph, the microporous structure of thephotopolymerized film can be clearly seen. For both polypyrrole filmtypes, the surfaces adhering to the substrates were smooth, shiny andfeatureless.

PRINTED WIRING BOARDS

The present photopolymerization process is ideally suited for thepreparation of conducting polymers as a direct metallization method forPWB production. A novel process for the production of double-sideprinted wiring boards, which involves photopolymerization of conductingpolypyrrole (or its derivatives), require only a few production stepsconsisting of:

(i) cleaning of a PWB substrate, drilling and deburring of holes;

(ii) application of photopolymerizable formulation;

(iii) formation of a dry negative photopolymerizable resist byair-drying;

(iv) exposure by UV light through a contact mask or by direct laserimaging. This step renders irradiated regions insoluble in acorresponding solvent, thus forming future current carrying lines; bothconductor lines and walls of through-holes are photopolymerized andbecome conductive;

(v) non-irradiated areas of the photopolymerizable film are washed offin a development process using benign chemicals such as acetone orwater;

(v) sensitization of conducting polymer lines and through-holes bydipping in a noble metal salt solution; and

(vi) electrodeposition of copper from acidic sulfate baths.

Once the desired conducting polymer patterns have been formed (stepsi-iv), additional steps must be taken to form a PWB. First, theconducting polymer is sensitized by immersion in a noble metal saltsolution where the noble metals undergo spontaneous deposition onto theconducting polymer. The process of sensitizing increases theconductivity of the polymer lines sufficiently to allow subsequentelectrodeposition of copper using conventional techniques. The preferredmetals are Palladium (Pd), Gold (Au), Copper (Cu) and Silver (Au). Themost preferred solution for sensitizing the conducting polymer is a0.01M aqueous palladium bromide (PdBr₂) solution.

Electrodeposition is typically performed in a copper sulfate bath (0.3MCuSO₄, pH=2.0). A cathodic current of about 100 mA is applied to theelectronically conducting polymer on the substrate with an aligatorclip. Under these conditions, a bright copper film can be seencontinuously growing outward from the clip along the conducting polymerlines. Over time, the copper layer will cover the entire surface of theconducting polymer lines and the layer will become thicker.

A new electroplating apparatus capable of plating photopolymerizedconducting polymer patterns has been designed which includes a rollingcylinder cathode for contacting the conducting polymer lines depositedon the board. As compared to a stationary cathode in contact with adiscrete point on the conducting polymer lines, the rolling cathodewould provide a more evenly distributed conductor layer.

Direct laser writing is usually a time consuming process, e.g., as inmaking photomasks, but in the proposed process many of the productionsteps are avoided. It is possible that this process could help buildinterconnecting vias in multilayer and complex PWB manufacturing, suchas in low-volume PWB production where high line resolutions arerequired.

FIG. 11 compares the basic steps of a conventional subtractive processand the direct metallization process of the present invention based onphotopolymerization of conducting polymers for the production ofdouble-sided printed wiring boards. The additive process differs fromthe subtractive process in that no eching is required and the circuitpattern is defined at the same time that through-hole connections aremade.

The process of the present invention is an additive process whichutilizes direct metallization of through-holes and conductors.Attractive features of the proposed direct metallization process for PWBfabrication are that many steps, normally required in conventionalprocesses, which are labor intensive or produce difficult to treathazardous waste, are avoided. The steps avoided by the present inventioninclude: (i) copper-foil lamination onto insulators; (ii) sensitizationof the entire board surface; (iii) electroless copper plating, and (iv)lift-off of the photoresist and surplus copper (foil) layer. If the PWBis to be through-hole plated, hole walls will be coated with a layer ofphotopolymerizable material in the same step as a dry-film is formed onthe surface of the PWB substrate. The subsequent copperelectrodeposition step will be the same as in conventional processes,except that the deposition bath will be optimized for deposition onto apolypyrrole surface.

EXAMPLE 9

A photograph of conducting polymer lines obtained by thephotopolymerization process and a line electrolytically coated withcopper after sensitization by dipping in a Pd containing solution ispresented in FIG. 12. Phtopolymerization conditions were optimized interms of line conductivity and line resolution, and comprised usingpyrrole and aniline as monomers, and cationic ferrocinium photoinitiator(IRGACURE™ 261 available from Ciba Geigy, located in Ardsley, N.Y.) inthe starting photopolymerization solution. Other experimental conditionswere as follows: fiberglass epoxy substrate; illumination with a UV lamp(Hg/Xe lamp, 81 mW/cm²) through a shadow mask; line thickness of 0.01";line spacing of 0.2"; photopolymerizable formulation consisted of 15 mMpyrrole, a pyrrole/silver nitrate molar ratio of 8:1; 15 mole percentaniline; photoinitiator concentration of 0.2 weight percent, and acetonewashing solvent. Sensitization was performed in 0.01M PdBr₂ solution,and electrodeposition in a typical copper sulfate bath (0.3M CuSO₄,pH=2.0).

EXAMPLE 10

Through-hole plating using a photopolymerized conducting polymer film asa substrate for electrodeposition of copper is shown in FIG. 13.

Both polymer and Cu-coated polymer lines passed the scotch-tape peel-offtest. Preliminary results on adhesion measurements (using diamondscratch test, Universal Adhesion Tester) performed on polymer/substrateand copper/polymer interfaces showed adhesion at both interfaces to besatisfactory for application in PWB manufacturing.

The present photopolymerization process for the synthesis of conductingpolymers can be implemented in: (a) high-volume automated PWBmanufacturing using UV irradiation through a contact mask applied tophotopolymerizable dry-films, and (b) low volume manufacturing ofcomplex, multilayer PWBs by direct laser imaging (DLI). The presentinvention is uniquely suited for adaptation to an automated PVBmanufacturing process, utilizing mostly standard equipment alreadydeveloped at PWB manufacturing facilities.

The process does not use copper foil laminate, because a conductingpolymer is photopolymerized directly on the PWB substrate. Further, noelectroless copper and noble metal plating steps are necessary, whichbrings additional cost savings. Because an electroless copper platingstep is avoided, the new process does not require hazardous wastetreatment from electroless plating baths, e.g. formaldehyde and metalcomplexes. Cost savings will be realized due to a reduction in directlabor costs, chemical costs, floor space requirements, lab analysis,ventilation requirements, etc.

However, the primary advantage of the present photopolymerizationprocess is that photopolymerized films can incorporate controlledamounts of anions, or additives during the photopolymerization process,in addition to anions needed for charge balance in the films. This opensup new perspectives in designing conducting polymer films, thuscontrolling desirable properties in the films. This is not possible inelectropolymerizations where only anions in amounts needed for chargebalance are incorporated into conducting polymer films. Addition ofsurfactant additives to monomer solutions containing other anions forelectropolymerization may cause blocking of the electrode surface andthus prevent electropolymerization from taking place.

It will be understood that certain combinations and subcombinations ofthe invention are of utility and may be employed without reference toother features in subcombinations. This is contemplated by and is withinthe scope of the present invention. As many possible embodiments may bemade of this invention without departing from the spirit and scopethereof, it is to be understood that all matters hereinabove set forthor shown in the accompanying drawings are to be interpreted asillustrative and not in a limiting sense.

What is claimed is:
 1. A composition, comprising:a) an electronicallyconducting polymer matrix comprising a polymer selected frompolypyrrole, polyaniline, polythiophene and mixtures thereof havingsilver grains uniformly disbursed throughout; and b) an ionicallyconducting ion exchange polymer homogeneously distributed in the polymermatrix.
 2. The composition of claim 1, wherein the electronicallyconducting polymer matrix comprises polypyrrole.
 3. The composition ofclaim 2, wherein the polypyrrole is photopolymerized from pyrrole andsilver salt in a pyrrole:silver salt molar ratio between about 2:1 andabout 100:1.
 4. The composition of claim 3, wherein the pyrrole:silversalt molar ratio is about 8:1.
 5. The composition of claim 4, whereinthe perfluorinated sulfonic acid polymer concentration is less thanabout 10 weight percent of the polymer matrix.
 6. A polymer matrix thatis electronically and ionically conducting, comprising:a) polypyrrolethat is photopolymerized from pyrrole and silver salt; and b) aperfluorinated sulfonic acid polymer that is incorporated generallyhomogeneously into the photopolymerized polypyrrole, wherein the weightratio of perfluorinated sulfonic acid polymer to polypyrrole is lessthan about 0.1 wherein said polypyrrole has silver grains distributedthroughout.
 7. The composition of claim 6, wherein the pyrrole andsilver salt are photopolymerized in a pyrrole:silver salt molar ratiobetween about 2:1 and about 100:1.
 8. The composition of claim 6 whereinthe pyrrole and silver salt are photopolymerized in a pyrrole:silversalt molar ratio of about 8:1.
 9. The composition of claim 3, whereinthe silver salt is selected from silver tosylate, silver perchlorate,silver tatrafluoroborate, silver nitrate, and mixtures thereof.
 10. Thecomposition of claim 3, wherein the silver salt is silver nitrate. 11.The composition of claim 6, wherein the silver salt is selected fromsilver tosylate, silver perchlorate, silver tatrafluoroborate, silvernitrate, and mixtures thereof.
 12. The composition of claim 6, whereinthe silver salt is silver nitrate.
 13. A composition, comprising:a) anelectronically conducting polymer matrix comprising a polymer selectedfrom polypyrrole, polyaniline, polythiophene and mixtures thereof havingsilver grains uniformly disbursed throughout; and b) a perfluorinatedsulfonic acid polymer homogeneously distributed in the polymer matrix.14. The composition of claim 13, wherein the electronically conductingpolymer comprises polypyrrole.
 15. The composition of claim 14, whereinthe polypyrrole is photopolymerized from pyrrole and silver salt in apyrrole:silver salt molar ratio between about 2:1 and about 100:1. 16.The composition of claim 15, wherein the pyrrole:silver salt molar ratiois about 8:1.
 17. The composition of claim 15, wherein the silver saltis selected from silver tosylate, silver perchlorate, silvertatrafluoroborate, silver nitrate, and mixtures thereof.
 18. Thecomposition of claim 15, wherein the silver salt is silver nitrate.